Three-dimensional printing is a process of making a three-dimensional solid object of virtually any shape from a digital model. One approach to three-dimensional printing uses an additive process in which one or more printheads eject successive layers of material on a substrate in different shapes. This approach to three-dimensional printing is also known as additive manufacturing. The substrate is either supported on a platform that can be moved in either one, two, or three dimensions by operation of actuators operatively connected to the platform. Additionally or alternatively, the printhead or printheads are also operatively connected to one or more actuators for controlled movement of the printhead or printheads to produce the layers that form the three-dimensional object. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
The production of a three-dimensional object with these printers can require hours or, with some objects, even days. One issue that arises in the production of three-dimensional objects with a three-dimensional printer is inconsistency between the actual dimensions of the printed part and the intended dimensions of the printed parts. These inconsistencies arise because the ejected ink material can flow away from its intended position when jetting onto the growing part. Other factors include thermal expansion and/or contraction of the material as hot ink is ejected onto the part and then is cooled or cured. During printing of an object, one or more inkjets can deteriorate by ejecting the material at an angle, rather than normal, to the printhead, ejecting drops that are smaller or larger than an inkjet should eject, or by failing to eject any drop at all. Other sources of error that occur during object printing include mechanical runout, mechanical shrinkage of the ejected material, vibration, and the like. Dimensional accuracy of an object is currently controlled by monitoring and verifying the accuracy of the movement of the support platform and/or the printhead or printheads. The sources of error identified above, may not be detected from the monitoring of the support platform or printhead(s) movement. If one or more of these sources for error accumulate during object printing, the quality of the printed object may require the object to be scrapped. Because the print jobs can require many hours or multiple days to produce objects, this scrapping of objects can be expensive and time consuming. A printer capable of detecting errors in an object being produced and correcting them during printing would be advantageous.